This invention relates to a heat-sensitive transfer recording material, more particularly to a heat-sensitive transfer recording material which can transfer a colorant by the heat generated by irradiation of photoenergy by, for example, laser, etc. to form a sharp image on an image-receiving material.
As the method for obtaining a color hard copy, investigations have been made about color recording techniques using ink jet, electrophotography, heat-sensitive transfer, etc.
Among these, particularly the heat-sensitive transfer system has such advantages as easy operation and maintenance, possibility of miniaturization of the apparatus, reduction of cost, and further inexpensive running cost, etc.
The heat-sensitive transfer recording system includes two types of systems. One is the system in which the transfer sheet (also called heat-sensitive transfer material) having a heat-meltable ink layer on a support is heated by a heat-sensitive head to have the above ink transferred by melting onto a transferable sheet (also called image-receiving material), and the other is the thermal diffusion transfer system (including the sublimation transfer system) in which a transfer sheet having an ink layer containing a thermally diffusible dye (including sublimable dye) on a support is heated by a heat-sensitive head to transfer the above thermally diffusible dye onto a transferable sheet. Of these, the thermal diffusion transfer system is more advantageous for full color recording, because the tone of image can be controlled by varying the amount of the dye transferred depending on the change in thermal energy of the heat-sensitive head.
In the prior art, as the heating method of a heat-sensitive transfer recording material, there have been generally employed the methods using a heat-generating body such as thermal head, etc., and the method of using a laser as the heat energy source has been also known.
In the method using a laser, when a heat-sensitive transfer recording material is exposed to laser beam, the laser beam is converted to heat energy, whereby the colorant in the vicinity exposed is heated, and the colorant corresponding to such heating is heat transferred to form an image in the image-receiving material.
The image forming method according to this method is disclosed in U.K. Patent No. 2,083,726A and Japanese Unexamined Patent Publication No. 2074/1990.
In this method, a substance which absorbs strongly the laser wavelength (laser absorbing substance) is contained in the heat-sensitive transfer recording material, and the laser absorbing substance absorbs photoenergy to convert it efficiently to heat energy.
As the above-mentioned laser substance, carbon and a specific IR-ray absorbing substance have been employed.
However, when carbon is used, since it is added in the form of fine particles, carbon particles are liable to be agglomerated, and hence there is the problem that the quality of the image by transfer of the colorant tends to be lowered.
On the other hand, when an IR-ray absorbable cyanine dye disclosed in Japanese Unexamined Patent Publication No. 2074/1990 is used, due to poor stability of the IR-ray absorbing dye itself, the density of the IR-ray absorbing dye will be lowered by heat, humidity or light, etc. during storage of the heat-sensitive transfer recording material, whereby there is involved the problem that the recording sensitivity with laser beam of the heat-sensitive transfer recording material may be sometimes deteriorated.
Further, carbon and the above-mentioned IR-ray absorbing dyes were also themselves transferred into the image-receiving material, thus having the problem of deteriorating the quality of image.
Therefore, an object of the present invention is to solve the problems as mentioned above of the heat-sensitive transfer recording material which performs image recording by use of a light such as laser beam.